1. Field of the Invention
This invention relates to a method for making a vacuum package filled with granular product, in which a package made from a flexible packaging material and filled with a granular product is evacuated and sealed hermetically.
2. Description of the Related Art
A method of vacuum packing material disclosed in U.S. Pat. No. 4,845,927. According to this known method, a package open at the top is produced from a sheet of flexible film and subsequently filled with a loose granular material. The filled package is placed in a vacuum chamber in which the package is subjected to vacuum. After the package has attained the desired degree of vacuum, the package is heat-sealed at the top using welding jaws arranged in the vacuum chamber. The package, now hermetically sealed, is then removed from the vacuum chamber.
From the point of view of efficiency and economy, it is desired that the volume of the vacuum chamber be kept as small as possible. Accordingly, the volume of the package to be evacuated is preferably made as small as possible by already folding up the filled package as much as possible before it is placed in the vacuum chamber. Moreover, in that case it is not necessary to arrange folding means in the vacuum chamber. In that case, the vacuum chamber need only contain the welding jaws which are necessary to hermetically seal the package which is already folded up completely. This means that the package is evacuated through a narrow gap left open in the top of the package. While the package is being evacuated in a short time, a high outflow velocity of gasses to be removed from the package arises in the gap. In the case of a granular structure of the filling in the package, in particular if the filling is fine-granular or in powder form, a problem occurs in that granules of material are sucked from the package and find their way into the vacuum chamber and contaminate it. The entrained granules may also stick to the inside wall at the top of the package, thereby impeding the sealing of the package and causing leakages.